Evaluation of the positional quality of terrestrial laser scans for architectural applications

Abstract

A prominent theme currently in architecture and construction is reality capture, a process of digitizing the real world using different 3D measurement technologies, allowing the expression of reality at different stages of a project and consisting of an important tool in the construction of systems. BIM (Building Information Modeling). One of the main pieces of equipment for obtaining this 3D data is the Terrestrial Laser Scanners (TLS) that allow the generation of point clouds. However, TLS and laser scanning practice have limitations like any measurement instrument. Therefore, the collected observations contain uncertainties that must be evaluated for data in the digital modeling of the object of interest. In this way, it is necessary to evaluate the positional quality of the coordinates obtained in a laser survey so that it is possible to understand how they will propagate in the final product. This work presents a methodology for verifying the quality of terrestrial laser scan coordinates using the TLS BLK360 Leica. Control points were used to record and determine the data reference system. Subsequently, the coordinates of the checkpoints recorded in the point clouds were compared with the data obtained by a topographic survey with the high precision Leica TS15 total station and statistically evaluated. The estimated quality of the recorded cloud passes through the interpolation of the coordinates of the centers of the control targets, as these are compared with the coordinates obtained through positioning by three-dimensional irradiation using the total station. The interpolation method and the cloud density influenced the assessment of positional quality in the recorded cloud. They used high sampling density with the TLS and interpolation through the average values for the coordinates of the targets. The positioning quality was better than 6mm for the present case study.